Lead-free and arsenic-free niobium phosphate optical glass

Abstract

The lead-free, arsenic-free, preferably gadolinium-free and fluorine-free, optical glass has a refractive index of 1.86≦nd≦1.95, an Abbe number of 19≦vd≦24, a transformation temperature of ≦595° C., preferably ≦550° C., good crystallization stability, good processing properties and production properties. The optical glass is free of Na2O, frre of B2O3 and has a composition (based on oxide content in % by weight) of P2O5, 14-31; Nb2O5, 22-50; Bi2O3, 5-36; WO3, >10-25; GeO2, 0-14; Li2O, 0-6; K2O, 0-6; Cs2O, 1-7; MgO, 0-6; CaO, 0-6; SrO, 0-6; BaO, 0-6; ZnO, 0-6; TiO2, 0-4; Σ alkali oxides, 2-12; Σ alkaline earth oxides, 0-10; Σ Nb2O5, WO3, Bi2O3≦50 and fining agents, 0-2.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a lead-free and arsenic-free and preferably fluorine-free niobium phosphate optical glass, to the use of such a glass in the fields of mapping, projection, telecommunication, optical communication engineering, mobile drive and laser technology, as well as to optical elements and so-called “preforms” of such optical elements, respectively.[0003]2. Related Art[0004]In recent years the trend in the market in the fields of optical and opto-electronic technologies (application fields; mapping, projection, telecommunication, optical communication engineering, mobile drive and laser technology) is toward more and more miniaturization. This is manifested in smaller and smaller finished products and of course demands increasing miniaturization of the individual structural members and components of such finished products. For the producers of optical glass this development translates into a defini...

AI Technical Summary

Benefits of technology

[0030]It is an object of the present invention to provide an optical glass, which has desired and advantageous optical properties (nd / νd) and low transformation temperatures, and particularly which, because of ecological considerations, is free of PbO, TI2O, TeO2, and As2O3 and preferably free of SiO2 and / or B2O3 and / or Na2O and / or fluorine. Most preferred glasses are free of the volatile compound B2O3.

[0033]It is another object of the present invention to provide an optical glass, which has good meltability and processability and sufficient crystallization stability, which enables production in continuously conducted aggregates.

[0041]The glass according to the present invention has the same optical state, such as the Abbe number and the refractive index, as known optical glass of similar glass families. However, the glass of the invention is characterized by good meltability and processability, as well as by good environmental compatibility.

[0043]In addition, the combination of the crystallization stability and the viscosity temperature profile of the glasses according to the present invention may facilitate a thermal (further) treatment (pressing and / or re-pressing) of the glasses, almost without any problems.

Problems solved by technology

At the same time increased pricing pressure on the glass manufacturers arises from the re-processors, since the production of such smaller components made of block and / or ingot glass produces a noticeably greater percentage of waste.

Also a higher operating expense is required for processing such miniaturized parts than for bigger components.

Because of the required high accuracy of geometries, high-grade precision instruments and therefore expensive mold materials have to be used for such a pressing procedure.

The lifetimes of such molds greatly affect the profitability of the products and / or materials produced.

The prior art already describes glasses with a similar optical state or with a comparable chemical composition, but these glasses have huge disadvantages.

In particular, many of the glasses contain higher proportions of SiO2, which is a network forming agent and therefore increases the transformation temperature of the glass, causes a longer viscosity curve and reduces the refractive index and / or the amounts of components, such as B2O3, Na2O and F, which readily can evaporate during the melting and burning process.

Thus an exact adjustment of the glass composition is difficult.

This evaporation is also disadvantageous during the pressing process, in which the glass is heated again and may deposit on the surface of the mold and on the glass.

According to the prior art larger amounts of the component titanium oxide (more than 4% by weight) are often used, however the tendency to crystallize will be increased undesirably and further the UV cut-off is shifted to longer wavelengths.

In every case the glass contains Na2O in an amount of at least 2.5% by weight, which is a disadvantage because of the aforesaid volatility of this component.

Such a high content of TiO2 shifts the UV cut-off to longer wavelengths, which is not desired, and promotes devitrification of the glass.

According to this application if amounts of niobium oxide are above 22% by weight an undesirable coloration of the glass occurs when it is exposed to UV light.

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